Engineering of Photosystem I Attachment to Titanium Oxide Nanostructures via Ferredoxin-Fusion Proteins

Ferredoxins (Fds) are iron-sulfur proteins that mediate electron transfer in a range of metabolic reactions. In the thylakoid membrane of photosynthetic organisms, Fd facilitates electron transfer from the stromal surface of photosystem I (PSI) to the ferredoxin Nicotinamide adenine dinucleotide phosphate oxidoreductase (FNR), which requires that Fd is capable of docking and transferring electrons between these two complexes. In applied photosynthesis, many efforts have been devoted towards re-directing these electrons into either a hydrogen-evolving catalyst or an electron-conducting semiconductor. In this study, the electrons from the PSI complex are directed to a titanium oxide (TiO₂) electrode, and Fd is used to facilitate the electron transfer. In doing so, three different TiO₂ binding peptides (TOBiP) were introduced to Fd in order to provide a specific affinity for TiO₂. The TOBiP-Fd fusion proteins were characterized for their ability to transfer electrons, and optimized for its attachment to TiO₂ nanoparticles. In addition, we have chemically crosslinked PSI to TOBiP-Fd and optimized the attachment of the PSI-Fd-TOBiP complex protein to TiO₂. In the future, we will test and optimize the photocurrent generated by the PSI-Fd-TiO₂ complex.